Eur J Med Res. 2026 Jan 8. doi: 10.1186/s40001-025-03826-3. Online ahead of print.
ABSTRACT
BACKGROUND: Knee osteoarthritis (KOA) is strongly associated with obesity, yet body mass index (BMI) fails to capture fat distribution or metabolic activity, limiting its utility in understanding KOA pathogenesis. Relative fat mass (RFM), a novel estimator of whole-body fat percentage derived from waist circumference and height, may provide a more accurate assessment of adiposity and its metabolic consequences.
OBJECTIVE: This study aimed to compare RFM and BMI in predicting MRI-detected structural changes in KOA and to investigate whether RFM statistically mediates the association between low-density lipoprotein (LDL) and cartilage degeneration.
METHODS: A retrospective analysis of 184 patients with symptomatic KOA was performed. BMI, RFM, and serum lipid profiles were measured. MRI assessments included cartilage volume, cartilage defects, and bone marrow lesions. Multivariable regression and ROC analysis evaluated predictive performance, while mediation analysis tested RFM’s role in the LDL-cartilage volume relationship.
RESULTS: RFM and BMI showed moderate correlation (r = 0.600, P < 0.001). RFM demonstrated significantly stronger associations with cartilage volume loss than BMI, particularly for patellar cartilage (RFM: β = -0.038, P < 0.001; BMI: P > 0.05). ROC analysis confirmed RFM’s superior predictive ability for patellar cartilage volume (AUC = 0.681 vs. 0.525). Mediation analysis revealed that the association between LDL and patellar cartilage volume showed a statistically significant indirect effect through RFM (indirect effect =- 0.071, 95% CI -0.133 to-0.008, proportion mediated = 72.4%). Sex-stratified analyses showed consistent associations in females (P < 0.001) with no significant RFM × sex interaction (P = 0.68).
CONCLUSION: RFM outperforms BMI in predicting structural damage in KOA, particularly cartilage volume loss. The identified statistically significant indirect pathway (LDL → RFM → cartilage volume) provides a novel framework for understanding how dyslipidemia may be associated with cartilage degeneration through adiposity, offering potential targets for metabolic intervention strategies in KOA prevention.
PMID:41508160 | DOI:10.1186/s40001-025-03826-3
